Knock when letting out clutch in first gear

[customsound79]

This may be such a random thing but I thought I would consult the vault of knowledge. This started about 2 weeks ago. When taking off from a stop I hear and feel a knock, pop, bump, whatever you want to call it. It only happens in first gear. I checked all the frame bolts and motor mounts and I'm a little concerned it's internal although it sounds structural. Anyone else have this experience?

[Mr Jensee]

Have you ever removed the rear wheel? There is a rubber cushion in the hub. If that has become damaged or deteriorated then that bump you feel and hear could be the metal plates colliding when you put it in gear. Eliminate that possibility before you go any further. If that is the reason you could be looking at a replacement wheel assembly.